ABSTRACT The long-term goal of the SPORE in Soft Tissue Sarcoma is to reduce the morbidity and mortality from soft tissue sarcoma by developing therapies targeted to specific molecular, genetic, epigenetic, and signaling pathway alterations or specific sarcoma type and subtype. To pursue this, we will focus our efforts on 4 broad translational research objectives: 1. Define shared and type-specific molecular mechanisms of sarcomagenesis to identify new rational therapeutic targets; 2. Define mechanisms of resistance to targeted therapies; 3. Clinically validate new therapeutic targets and treatments in soft tissue sarcoma patients and facilitate the development, recruitment, and application of clinical trials that serve both the adult and pediatric populations; 4. Discover specific molecular alterations and new biomarkers that predict outcome and response to targeted therapy. To achieve these goals, we have marshaled an integrated, multidisciplinary group of basic and clinical investigators, all armed with a unique resource, a clinicopathologic and outcomes database prospectively collected over a 35-year period. This database now contains data for over 11,840 patients treated for soft tissue sarcoma at MSKCC. The database is linked to an extensive sarcoma tissue/blood bank, which in turn is linked to an extensive multi-platform molecular genetic and epigenetic dataset and a collection of primary sarcoma cell lines and mouse xenograft/PDX models of human sarcoma. The SPORE is structured around 4 research projects, 4 cores, and career enhancement and developmental research programs. Each research project focuses on three or more of the 4 broad translational research goals listed above. RP-1 (GIST Resistance) aims to identify new therapeutic targets and develop new treatment strategies for imatinib- resistant GIST, including strategies for the largely pediatric subset with SDH-deficient GIST. RP-2 (CDK4 Targeting) seeks to identify a pre-treatment biomarker predictive of prolonged clinical response to CDK4 inhibitor therapy and to find drugs that can be combined with CDK4 inhibition to synergistically augment the senescence response. RP-3 (Oncogenic Pathways) seeks to determine the efficacy and molecular effects of inhibitors of mTOR, PI3K, MEK, and oncogenic translation (eIF4A), alone and in combination, in myxofibrosarcoma and undifferentiated pleomorphic sarcoma to develop new targeted treatment strategies. RP-4 (Functional Genomic Screens) will perform CRISPR-based functional genomic screens to uncover epigenetic and genetic vulnerabilities in synovial sarcoma with the aim of discovering drug targets for preclinical and clinical evaluation.